Which IGP uses hop count to determine route path?

• A. RIP
• B. OSPF
• C. IS-IS
• D. EIGRP

Answer: (A)

The concept being tested is the metric used by an IGP to choose routes. The one that determines the best path by hop count is RIP. In RIP, each hop adds one to the path cost, and the route with the fewest hops is preferred. There’s a practical limit of 15 hops; a route with 16 hops is considered unreachable, which helps prevent loops but limits how large a network RIP can efficiently scale to. This simple hop-based metric makes RIP easy to implement, but it doesn’t account for link speed or quality, so convergence is slower and scalability is limited compared to other IGPs.

OSPF, by contrast, uses a cost based on link bandwidth (faster links have lower cost), and IS-IS uses a similar bandwidth-informed cost. EIGRP employs a more complex, composite metric that incorporates multiple factors such as bandwidth and delay (and can include additional parameters).